One of the basic problems in the mineralization of dentin, enamel and bone is the quantification of the relative contribution of new dietary minerals versus old minerals that are derived from resorbed bone under normal, pathological and pharmacological-induced conditions. The distinction between the physiological regulation of the intake of new minerals and the regulation of the release and reuse of pre-existing minerals is not well understood at the present time. The objective of these studies is to investigate how dentin and enamel utilize new and pre-existing minerals (calcim and phosphorus) kinetically and spatially during various ages and experimental treatments. We have developed a kinetic procdure that will aid in quantifying the relative amount of mineral in new dentin an enamel that is derived from diet versus that derived from resorbed bone. This procedure involves extensively prelabelled animals where systemic recycling of the incorporated isotope predominates under steady state conditions. The specific aims are to: (1) quantify the accumulation of new (nonradioactive) mineral compared to the accumulation of old (radioactive) mineral over varying periods of time in young animals that have been repeatedly prelabelled, (2) describe microscopically the spatial distribution of calcium and phosphorus within the forming dentin and enamel, (3) correlate the kinetics with the spatial distribution of mineral in dentin and enamel as determined by microradiography and autoradiography. The above aims will be carried out using rats and guinea pigs under normal and experimental conditions: rachitic-induced conditions: vitamin D-deficiency, diphosphonate (EHDP); hyper-hormonal conditions parathyroid hormone, 1,25-diOH-vitamin D3; and chemical insults - high doses of fluoride or tetracycline. The understanding of the reutilization of pre-existing minerals by dentin and enamel from resorbed bone would provide a new biological basis for elucidating the mineralization of teeth under normal and pathological conditions.